JPH08265331A - Flow control device and flow control method - Google Patents

Abstract

(57) [Summary] [Purpose] In an ATM switching network, a switch node that does not have a flow control function can easily handle the flow data between computers without causing cell discard and efficiently handling transfer data between computers. A flow control device and a flow control method that can be added to the above. A cell having one cell input, a buffer for accumulating cells input from the cell input, and one cell output for outputting cells stored in the buffer, and a cell input from the cell input is Output from the cell output buffer empty information transmission cells to prevent overflow from the buffer, buffer empty information transmission cells input from the cell input, based on a predetermined quality assurance traffic parameters , Controlling the timing of outputting the cells accumulated in the buffer from the cell output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control device and a flow control method for adding a flow control function to a cell switch node having no flow control function for preventing discard due to cell congestion in an ATM switching network. .

[0002]

2. Description of the Related Art Currently, ATM (Asyncronou)
Researchers in communication technology around the world are energetically carrying out research on s Transfer Mode communication systems. In the ATM communication system, information is transferred and exchanged in fixed length packets called cells. In the ATM communication method, a high-speed cell switching can be performed by a cell switch by hardware, and an information transfer capacity per unit time that exceeds that of an existing communication network can be realized.

As a typical mounting form of a switch node for exchanging ATM cells, a structure called bookshelf type mounting as shown in FIG. 23 is considered. This configuration mainly consists of three types of elements: a switch board, an interface board, and a backplane. The interface board accommodates the interface points and has a transmission circuit and a reception circuit that match the specifications of the physical transmission path. By changing the type of the interface board, it is possible to easily accommodate physical transmission lines having different specifications in the switch node. The cells arriving from the interface point and input to the receiving circuit of the interface board are sent to the switch board via the backplane after being added with the routing tag. After being exchanged by the switch board according to the routing tag information, the cells are transferred again to the transmission circuit of the appropriate interface board via the backplane, and after the routing tag is deleted, the cells are output to the interface point.

The ATM communication system uses the VPI of the cell header.
(Virtual Path Identifier)
And VCI (Virtual Channel Iden
It is possible to logically set a plurality of concatenations on one physical transmission line by means of identification information called "tifer)". It is said that the statistical multiplexing effect of cells enables efficient use of the physical transmission line and setting of a connection with guaranteed quality. The quality referred to here is a cell discard rate, a cell transmission delay time, or the like.

In the case of a transmission path of a closed cell inside one switch node, the connection identifier is added to the cell together with a routing tag etc. as another method besides using the VPI and VCI of the cell header. It is also possible to identify by attaching a specific connection identifier. The connection identifier added in the node is V
By searching the table from the PI and VCI, it is added to the cell together with the routing tag in the receiving circuit of the interface board in the switch node, and after being replaced, it is deleted in the transmitting circuit of the interface board. VPI and VCI
Are uniquely assigned in the physical transmission path between the switch nodes, the switch node has the ability to rewrite the VPI and VCI values of the passing cell.

Up to now, the connection of which quality is guaranteed in the ATM network is CBR (Constant Bit).
Rate: Fixed bit rate) Connection or VBR
(Variable Bit Rate) Connection was the main. The CBR connection is a connection for transmitting traffic that has a constant cell transmission rate (also referred to as cell rate or band; the number of transmission cells per unit time) and is known in advance.
The R connection is a connection in which the transmission rate of the cell is not constant, but the traffic characteristics such as the maximum value (peak rate) and the average value (average rate) are known in advance.

Basically, when a plurality of connections are multiplexed on one physical transmission line while maintaining sufficient quality, the sum of the peak rates of all the connections is below the band of the physical transmission line. Just do it. This method is called peak rate allocation. When only the CBR connection is assigned the peak rate, a sufficiently high utilization efficiency of the physical transmission line can be achieved. In the case of the VBR connection, peak rate allocation cannot increase the utilization efficiency of the physical transmission path. Therefore, from the nature of the traffic known in advance, a technique for improving the utilization efficiency while maintaining the quality by using the statistical multiplexing effect has been intensively studied.

However, considering ATM communication between computers, the nature of the traffic such as the average rate cannot be predicted in advance, and a large number of cells are momentarily transmitted, but no cells are transmitted at no time. There is a property called burst property. Therefore, it is difficult to improve the utilization efficiency of the network while guaranteeing the quality like CBR and VBR. In other words, the data transferred between computers is significantly reduced in network utilization efficiency when trying to guarantee the quality by peak rate allocation, etc. When statistical multiplexing effect like VBR is used, it is switched due to the burstiness of traffic. There is a problem in that a large number of cells arrive at an output port with a node at the same time and cell discard occurs due to buffer overflow.

Therefore, in recent years, flow control is performed between a terminal and a switch node and between a switch node and a switch node to guarantee the quality of transfer data between computers (particularly the quality regarding cell discard) to improve network utilization efficiency. Several methods have been proposed. When a device (switch node or receiving terminal) that has a flow control function on the receiving side overflows the buffer and is about to be discarded, the flow control on the transmitting side is performed before the cell is discarded by some method. Request devices with functions (switch nodes and transmission side terminals) to suppress cell transmission. In these flow control methods, the switch node must have a special mechanism for the flow control function.

It is difficult to add this function of the conventional switch node that does not assume the flow control function because the switch node replacement function is performed by hardware. Since both the switch board and the interface board require a fundamental configuration change, it was necessary to temporarily stop the operation in order to add the flow control function to the switch node in operation.

Further, when a new flow control method with good performance or a new flow control method for providing a new service is proposed and it becomes necessary to add a flow control function corresponding thereto, the switch is switched each time. The operation of the node may have to be interrupted. In addition, the CB that does not require the flow control function set in the interface board or the switch board in service must be replaced even if the function is changed / added to a small degree.
There was a risk that all connections, including R and VBR, would have to be disconnected.

Another problem is that a switch node that accommodates a large number of interface points may require a flow control function based on a different system for each interface point, or an interface point that does not require a flow control function. There is a possibility that it exists, and if you try to handle all flow control mechanisms so that it can handle all of them,
There is a problem that the cost of the switch node becomes very large.

By the way, in order to pass a connection with flow control to a switch node which does not have a flow control function, a method by rate control and a method called tunneling have been proposed.

The rate control method requires a function capable of adding congestion experience information to a switch node having no flow control function. The hardware scale to realize this function is
It is generally smaller than the scale of hardware that implements the flow control function. A typical method is as follows. When congestion occurs and the cell buffer in the switch node is about to overflow, it is a function of adding congestion experience information to a cell that has experienced congestion. An area for displaying the presence or absence of congestion is provided in the header of the ATM cell. The device having the downstream flow control function, which has received the cell displayed as having congestion experience, controls the device having the flow control function upstream of the congested switch node so as to suppress the output rate.

On the other hand, in the tunneling method, when a connection with flow control passes through a switch node that does not have the flow control function, a device having the flow control function upstream of the connection node uses the traffic parameter given in advance to establish the connection with flow control. This is a method of guaranteeing the quality of the section by changing the traffic of (1) to traffic that can guarantee the quality (for example, traffic with a limited peak rate) and passing the traffic.

The following problems are common to both the rate control method and the tunneling method.
If a large number of switch nodes that do not have the flow control function are inserted between devices that have the flow control function on the path of the connection with the flow control, or if the transmission distance becomes long and the cell transmission delay time becomes large, Whether the rate control or the tunneling is performed, it takes a long time until the flow control shows the effect. For example, if the cell buffer of a device with a downstream flow control function is about to overflow,
A device with a downstream flow control function sends control information to the upstream to request that cell transmission be suppressed, but if the cell transmission delay time is large, the flow control upstream from the device where congestion has occurred A large number of cells may be transmitted on the transmission path even while the control information arrives at the device having the function. Therefore, the congested device must have a large enough buffer to not discard them.
If the buffer amount is small, the flow control information must be transmitted so as to suppress the cell transmission in advance assuming the worst case, which has a drawback that the throughput performance is deteriorated.

Considering only the tunneling method, there are the following drawbacks (FIG. 24). For example, C1, C2, C3 output from a device having a flow control function
Quality is guaranteed when the three peak-rate limited traffics of the above are input from the three input ports of the switch node without the flow control function, exchanged, and output to one output port. Therefore, the output port requires a band of the sum of C1, C2, and C3. However, when the flow-controlled connection is mainly for transferring data between computers, this sum band is not always used effectively and cells are not always transmitted.
In such an instance, it may happen that most of the time this bandwidth is unused even though no other connection can use this band. Thus, the resources of the network could not be used efficiently.

[0018]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
When handling transfer data between computers on the TM network,
The switch node needs to have a flow control function, but it is difficult to add the function flexibly. Further, the conventional countermeasures in the case where the switch node does not have the flow control function also have the problems that the performance may be deteriorated and that the resources of the network cannot be effectively used.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a flow control device that can easily add a flow control function to a switch node that does not have a flow control function during operation, and It is to provide a flow control method.

[0020]

In order to achieve the above-mentioned object, in the present invention, an ATM switch provided with at least a plurality of input ports and a plurality of output ports provided between ATM exchanges via a transmission line. ATM with
In a flow control device connected to an exchange, an AT input from a specific input port among a plurality of input ports
ATM connected to an output port through which an M cell is output via an ATM switch and output from this output port
The ATM cells connected to the input port where the ATM cells are transmitted via the ATM switch to the output port connected to this next stage ATM switch are stored in a shared manner so that the cells are output to the next stage ATM switch. The ATM switch to the output port connected to the ATM switch of the preceding stage so that the buffer for performing the operation and the first buffer idle information transmission cell indicating the empty information in this buffer are transmitted to the ATM switch of the preceding stage. Is connected to the input port for transmitting the first buffer empty information transmission cell via the
A based on the buffer empty information of the second buffer empty information transmission cell transmitted from the M switch and the predetermined traffic quality assurance traffic parameter
And a control unit for controlling the output of the TM cell.

The other is an ATM switch provided with at least a plurality of input ports and a plurality of output ports provided through a transmission line between ATM exchanges, and a specific one of the plurality of input ports. The ATM cell input from the input port is connected to the output port output via the ATM switch, and the A output from this output port
The ATM cell is output to the output port connected to the ATM switch of the next stage so that the TM cell is output to the ATM switch of the next stage.
In a flow control method for flow control of an ATM switch having a buffer for accumulating and accumulating ATM cells connected to an input port for transmitting ATM cells via a switch, in a buffer input to an input port The first buffer vacant information transmission cell indicating the vacant information of No. 2 is transmitted from the ATM switch of the next stage by controlling the ATM switch so as to be transmitted to the output port connected to the ATM exchange of the preceding stage. Buffer empty information of the cell, the output of the ATM cell from the buffer is controlled on the basis of the buffer empty information of the cell and a predetermined traffic quality guarantee traffic parameter.

[0022]

By connecting the flow control device of the present invention to the input port and the output port of the switch node which does not have the flow control function, the device having the upstream flow control function and the flow control device of the present invention are connected to each other. Also, flow control can be performed between the flow control device of the present invention and a device having a downstream flow control function.

Further, the flow control device of the present invention outputs the data transmission cell based on the traffic parameter which can guarantee the quality in the switch node having no flow control function. As a result, transfer data between computers can be efficiently handled without causing cell discard in the ATM network.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, an outline of the operation of the flow control device will be described below. The flow control device of the present invention works effectively by connecting to a switch node that does not have a flow control function. FIG. 1 is a conceptual diagram showing the flow of flow control information in an ATM network equipped with the flow control device of the present invention.

The data transmission cell belonging to the connection with flow control is a device 1 (terminal, switch node with flow control function, or book) having a flow control function upstream of the flow control device of the present invention (illustrated on the left side of FIG. 1). From the flow control device of the invention), the flow control device 4 of the present invention is reached via one or more switch nodes having no flow control function. On the other hand, the buffer empty information transmission cell is transferred from the flow control device 4 of the present invention to the device 1 having the flow control function, which is located upstream of the flow control device of the present invention. The buffer empty information transmission cell transfers flow control information such as buffer empty information in the flow control device 4 of the present invention.

When a data transmission cell passes through a switch node having no flow control function, congestion experience information may be attached to the data transmission cell at the switch node. From the congestion experience information, the flow control device knows that congestion has occurred upstream. The flow control device 4 of the present invention reflects the content of the congestion experience information in the buffer empty information transmission cell to be transferred to the upstream side, and transfers it to the upstream device 1 having the flow control function.

The device 1 having the flow control function, which has received the buffer empty information transmission cell, controls the transmission of the cell based on the flow control information and the congestion experience information contained in the cell so that the data transmission cell is not discarded. be able to.

As described above, flow control is performed between the flow control device 4 of the present invention and the device 1 having the upstream flow control function so that cell discard is not generated. Similarly, the flow control is performed between the flow control device of the present invention and a device 2 (shown on the right side of FIG. 1) having a downstream flow control function which is connected via one or more switch nodes having no flow control function. Do.

The flow control device 4 of the present invention has a quality assurance traffic parameter so that the data transmission cell is not discarded in the switch node 2 having no downstream flow control function. The quality assurance traffic parameters are predetermined in correspondence with the downstream devices having flow control functions.

The flow control device of the present invention uses the traffic quality assurance traffic parameters and the flow control information and congestion experience information contained in the buffer empty information transmission cells transferred from the device having the downstream flow control function, Controls the transmission of data transmission cells.

By performing flow control on all routes from the terminal on the transmitting side to the terminal on the receiving side via some devices having the flow control function, the cells can be transferred without being discarded. it can.

One flow control method of the above flow control device will be described below. A credit method is known as one of the methods for adjusting the cell output so that the buffer inside the flow control device does not overflow. This is a method of notifying the free space amount (credit) of a buffer inside a device having a downstream flow control function, and sending cells so that the number does not exceed the number. A buffer vacant information transmission cell having information such as "N cells are output from the connection-by-connection buffer, so that only N cells can be stored in the connection-by-connection buffer" is transferred from the downstream device having a flow control function. come. Unless more data transmission cells than the number of cells permitted from the downstream are transferred, the cells are not discarded from the internal buffer of the device having the downstream flow control function.

When the flow control device of the present invention performs credit type flow control, there is a delay time when transmitting the buffer empty information transmission cell from the downstream side to the upstream side. Need to have. Further, it is necessary to provide a mechanism for periodically synchronizing the credit information in order to prevent the credit information from being lost between the upstream and the downstream due to cell discard due to a bit error. This mechanism may be provided in the flow control device of the present invention with the same mechanism as the credit information synchronization mechanism of the switch node with the flow control function, which has been discussed by many researchers.

Another method of adjusting the cell output so that the buffer does not overflow is a method called a rate control method. This requires a function to notify a switch node having no flow control function of the congestion state of the switch node directly or indirectly to a device having an upstream flow control function.

For example, the switch node has a function of adding congestion experience information to a cell that has experienced congestion. The device having the flow control function, which has received the cell in which the congestion experience is displayed, reflects the content of the display and transfers the buffer empty information transmission cell to the device having the flow control function in the upstream.

Further, for example, a device having a flow control function controls in the same direction as the data transmission cells at intervals based on a certain algorithm (for example, a fixed time interval or every time a fixed number of data transmission cells are transferred). Transfer cells. The device having the downstream flow control function loops back its control cell to the upstream. (A control cell that loops back is also called a buffer empty information transmission cell.)
In the switch node through which the control cell or the buffer vacant information transmission cell passes, the information "congestion state (or non-congestion state)" is written in the cell according to the congestion state. When performing this control method, the flow control device of the present invention writes the information reflecting the state of the internal buffer into the cell that loops back. The flow control device of the present invention which handles this method transfers the control cell together with the data transmission cell to the device having the downstream flow control function for flow control with the device having the downstream flow control function. Need to have the ability to.

The upstream flow control device of the present invention, which has received the buffer empty information transmission cell, controls the transmission of the cell based on it. If there is congestion, the rate of the data transmission cell is reduced, and if there is no congestion, the rate of the data transmission cell is increased.

When the flow control device of the present invention uses the rate control method, it is necessary that the congestion experience information added to the cell by the switch node having no flow control function upstream thereof is not transferred downstream. This is to prevent the downstream device having the flow control function of the flow control device of the present invention from erroneously determining the congestion status due to irrelevant congestion experience information.

Still another method is considered as the rate control method. In the rate control method in which the device having the flow control function transfers the control cell in the same direction as the data transmission cell, when the control cell or the buffer empty information transmission cell passes through each switch node, the cell is When the number of cells stored in the buffer is to be read out, write "how much compared to a target value with a time ratio when it is not zero", or write "cell transmission rate". The switch node has the function of writing the information "Please keep this rate".

Upon receiving the buffer empty information transmission cell, the upstream flow control apparatus of the present invention calculates the transmission rate of a new cell based on the flow control apparatus. As described above, various methods have been studied for the flow control method in the ATM communication method, but the flow control device of the present invention works effectively regardless of the flow control method.

The flow control device of the present invention is roughly classified into the following five configuration methods. As a first configuration of the present invention, FIG. 2 shows an example of the connection between the first configuration of the present invention and a switch node having no flow control function. The flow control device of the present invention is connected to one or more switch nodes having no flow control function. Regarding the connection method, the output port of the switch node is connected to the cell input of the present invention, and the cell output of the present invention is connected to the input port of the switch node.

As a second configuration of the present invention, FIG. 3 shows an example of the connection between the second configuration of the present invention and a switch node having no flow control function. The flow control device of the present invention is connected to one or more switch nodes having no flow control function. As for the connection method, similar to the first configuration, the output port of the switch node is connected to the cell input of the present invention, and the cell output of the present invention is connected to the input port of the switch node.

As a third configuration of the present invention, FIG. 4 shows an example of the connection between the third configuration of the present invention and a switch node having no flow control function. The flow control device of the present invention is connected to one or more switch nodes having no flow control function. The flow control device of the present invention has an extended cell input and an extended cell output in addition to a cell input and a cell output. The connection method is such that the output port of the switch node is connected to the cell input of the present invention, the cell output of the present invention is connected to the input port of the switch node, and an expanded cell output of the present invention is expanded to another of the present invention. Connect to cell inputs together.

As a fourth configuration of the present invention, FIG. 5 shows an example of the connection between the fourth configuration of the present invention and a switch node having no flow control function. The flow control device of the present invention is connected to one or more switch nodes having no flow control function. The connection method is the same as in the first configuration. The difference from the first configuration is that the flow control devices of the present invention are connected to each other.

As a fifth configuration of the present invention, FIG. 6 shows an example of the connection between the fifth configuration of the present invention and a switch node having no flow control function. The flow control device of the present invention is connected to one or more switch nodes having no flow control function. The connection method is the same as in the fourth configuration. The difference from the fourth configuration is that a flow controller input switch is provided on the input side of the flow controller of the present invention. The flow control device input switch has an expanded cell input and an expanded cell output, and the flow control device is connected via the expanded cell input and the expanded cell output.

A specific example of the functional configuration of each configuration will be described later. First, the flow of cells in each configuration will be described. FIG. 7 shows the flow of the data transmission cell of the first configuration of the present invention and the flow of the buffer empty information transmission cell for controlling it. Both the data transmission cell and the buffer empty information cell are input to the cell input of the flow control device of the present invention. From the cell output, both the data transmission cell and the buffer empty information transmission cell generated in the flow control device of the present invention are output. In the figure, two arrows are input and two are output to the flow control device of the present invention, but this represents a logical cell path, and the actual physical transmission path is one input and one output. Is.

The ATM connection is bidirectional. The flow of the data transmission cell in the opposite direction with the same connection as the flow of the data transmission cell shown by the solid line in FIG. 7 may be the same route as the flow of the buffer empty information transmission cell shown by the dotted line. The flow of the buffer empty information transmission cell that controls the flow of the data transmission cell may be the same route as the flow of the data transmission cell indicated by the solid line.

FIG. 8 shows the flow of the data transmission cell of the second configuration of the present invention and the flow of the buffer empty information transmission cell for controlling it. The second configuration of the present invention is
There are two sets of cell input, cell output and buffer.

The data transmission cell input from the upper cell input of the flow control device of the present invention is accumulated in the upper buffer and output from the upper cell output. The cell output from the upper cell output is controlled by the buffer empty information transmission cell input from the lower cell input.

Further, by detecting the state of the upper buffer,
Since the cell input from the upper cell input is controlled, the buffer empty information transmission cell is output from the lower cell output. The flow of data transmission cells in the same connection and in the opposite direction as the flow of data transmission cells shown by the solid line in FIG. 8 may be the same path as the flow of buffer empty information transmission cells shown by the dotted line. The flow of the buffer empty information transmission cell that controls the flow of the data transmission cell may be the same route as the flow of the data transmission cell indicated by the solid line.

Data transmission cells input from the lower cell input of the present invention are accumulated in the lower buffer and output from the lower cell output. The cell output from the lower cell output is controlled by the buffer empty information transmission cell input from the upper cell input.

Also, by detecting the state of the lower buffer,
Since the cell input from the lower cell input is controlled, the buffer empty information transmission cell is output from the upper cell output. The configuration example of FIG. 8 can use the band for the data transmission cell approximately twice as much as the configuration example of FIG. 7.

FIG. 9 shows the flow of the data transmission cell of the third configuration of the present invention and the flow of the buffer empty information transmission cell for controlling it. The third configuration of the present invention is
There are two sets of cell input, cell output and buffer, and two sets of extended cell input and extended cell output.

Data transmission cells input from the upper cell input or the upper expansion cell input of the present invention are accumulated in the upper buffer and output from the upper cell output or the upper expansion cell output.

The cell output from the upper cell output is controlled by the buffer empty information transmission cell input from the lower cell input. Also, to detect the state of the upper buffer and control the cell input from the upper cell input,
The buffer empty information transmission cell is output from the cell output on the lower side.

The cell output from the upper extended cell output is
It is controlled by the buffer empty information transmission cell input from the extended cell input on the lower side. Further, since the state of the upper buffer is detected and the cell input from the upper extended cell input is controlled, the buffer empty information transmission cell is output from the lower extended cell output.

The flow of data transmission cells having the same connection as the flow of data transmission cells shown by the solid line in FIG. 9 but in the opposite direction may be the same route as the flow of the buffer empty information transmission cells shown by the dotted line. The flow of the buffer empty information transmission cell that controls the flow of the data transmission cell may be the same route as the flow of the data transmission cell indicated by the solid line.

Data transmission cells input from the lower cell input or the lower expansion cell input of the present invention are accumulated in the lower buffer and output from the lower cell output or the lower expansion cell output. .

The cell output from the lower cell output is controlled by the buffer empty information transmission cell input from the upper cell input. Also, to detect the state of the lower buffer and control the cell input from the lower cell input,
The buffer empty information transmission cell is output from the upper cell output.

The cell output from the lower extended cell output is
It is controlled by the buffer empty information transmission cell input from the upper extended cell input. Further, since the state of the lower buffer is detected and the cell input from the lower extended cell input is controlled, the buffer empty information transmission cell is output from the upper extended cell output.

By setting the connection as shown in FIG. 9, the buffer empty information transmission cells can be transferred and the flow control can be realized even between the flow control devices of the present invention connected by the expansion cell input and the expansion cell output.

FIG. 10 shows the flow of the data transmission cell of the fourth structure of the present invention and the flow of the buffer empty information transmission cell for controlling it. The data transmission cell input from the cell input of the flow control device of the present invention on the upper side is accumulated in the buffer on the upper side and output from the cell output on the upper side.

The cell output from the upper cell output is controlled by the buffer empty information transmission cell input from the lower cell input. Also, to detect the state of the upper buffer and control the cell input from the upper cell input,
The buffer empty information transmission cell is output from the cell output on the lower side.

The control information obtained from the input buffer empty information transmission cell is transferred via the interface connecting between the flow control devices of the present invention. In addition, the information regarding the state of the buffer in the flow control device is also transferred via the interface connecting the flow control devices.

The ATM connection is bidirectional. The flow of data transmission cells having the same connection and opposite direction to the flow of data transmission cells shown by the solid line in FIG. 10 may be the same route as the flow of buffer empty information transmission cells shown by the dotted line.
The flow of the buffer empty information transmission cell that controls the flow of the data transmission cell may be the same route as the flow of the data transmission cell indicated by the solid line.

FIG. 11 shows an example of the flow of the data transmission cell of the fifth configuration of the present invention and the flow of the buffer empty information transmission cell for controlling it. The flow control device of the fifth configuration has a configuration in which a flow control device input switch is provided on the input side of the fourth configuration of the present invention.

The cell input from the cell input of the flow control device of the present invention is transferred to the inside of the flow control device of the present invention by the flow control device input switch, or
It is transferred to the expansion cell input of the adjacent flow control device via the expansion cell output. The cell input from the expanded cell input is also replaced by the flow controller input switch in the same manner as the cell input from the cell input.

The control information obtained from the input buffer empty information transmission cell is transferred via the interface connecting between the flow control devices of the present invention, which is the same as the fourth configuration of the present invention. Further, the information regarding the state of the buffer in the flow control device is transferred via the interface connecting the flow control devices, which is the same as the fourth configuration of the present invention.

The ATM connection is bidirectional. The flow of the data transmission cell in the opposite direction to the flow of the data transmission cell shown by the solid line in FIG. 11 may be the same route as the flow of the buffer empty information transmission cell shown by the dotted line.
The flow of the buffer empty information transmission cell that controls the flow of the data transmission cell may be the same route as the flow of the data transmission cell indicated by the solid line.

Next, an example of a connection setting method will be described below. A connection setting method applicable to the first, second, third, fourth and fifth configurations of the present invention will be described with reference to FIG.

In FIG. 12, connections are input one by one from the three input ports of the switch node having no flow control function (C1, C2, C3), and the flow is re-routed via the flow control device of the present invention. 3 when output from one output port with a switch node that does not have a control function
The paths of the data transmission cells on one connection are shown.

The peak rates at the time of inputting the three connections C1, C2 and C3 to the switch node are 0.
Set to 3. The band of the input / output port of the switch node is 1.0 here. C1, C2, and C3 do not normally transfer cells, but occasionally transfer cells at a peak rate.

Considering the case where a data transmission cell is simultaneously transferred at a peak rate to three connections, the output port of the switch node originally requires a total bandwidth of 0.9 for the three connections. If the sum of the peak rates of the output ports is within 1.0, cell discard does not occur. (Actually, there are fluctuations in the cell arrival intervals, so it is necessary to give some margin to the sum of peat rates.
Here, for simplicity of description, it is assumed that if the sum is within 1.0, then congestion does not occur and quality can be guaranteed. )
If the probability of data transmission cells being transferred at the peak rate over three connections at the same time is low, it is considered that the output port bandwidth of the switch node of only 0.3 is almost sufficient, but multiple connections happen to occur. When data transmission cells are transferred at the peak rate at the same time, a large number of waiting cells are generated in the buffer in the switch node, and in some cases, cell discard due to buffer overflow may occur.

As shown in FIG. 12, the total peak rate of the data transmission cells transferred through the three connections is determined by the traffic parameters given in advance when the data is transmitted to the flow control device of the present invention and output. Is 0.3
Limit not to exceed. As a result, the band usage efficiency at the output port of the switch node is improved.
In addition, a margin of 0.7 band is generated, and another connection can use it.

The flow control device of the present invention monitors the state of the buffer therein, and transmits buffer empty information for controlling the transfer of data transmission cells to the device having the upstream flow control function so that the buffer does not overflow. Transfer cells. By this control, even when data transmission cells arrive at a peak rate of 0.3 from a plurality of connections at the same time, the cell is not discarded due to the buffer overflow.

A connection setting method applicable to the first, second, third, fourth and fifth configuration examples of the present invention will be described with reference to FIG. FIG. 13 shows a plurality of switch nodes (two in the case of FIG. 13) having no single flow control function.
The flow control device according to the present invention is connected and the data transmission cells are transferred via the plurality of flow control devices.

In FIG. 13, four connections C1, C2, C3 and C4 are input to the switch node having no flow control function. The peak rates are 0.
6, 0.3, 0.3 and 0.3. These four connections are output from one output port having a switch node with a total bandwidth of 0.6. Since the sum of the peak rates of these four lines exceeds 1.0, this cannot be realized by one flow control device of the present invention like the connection setting of FIG. 12 described above.

In FIG. 13, C2, C3 and C4 are first routed to the flow controller a of the present invention.
Here, the total peak rate of these three connections is reduced to 0.3 using the method of FIG. afterwards,
The output is once routed to the flow control device b via the switch node. Further to the flow control device b,
The peak rate of the total of C1, C2, C3, and C4 finally output from the flow control device b can be set to 0.6 by routing C1.

With respect to the connections C2, C3 and C4, a buffer empty information transmission cell is transferred from the flow control device b to the flow control device a depending on the state of the buffer of the flow control device b of the present invention.

By routing the connections as shown in FIG. 13, it becomes possible to handle more connections than in the case of FIG. More connections can be handled by connecting the flow control device of the present invention to more switch nodes that do not have flow control functions.

FIG. 14 illustrates a connection setting method applicable to the third configuration of the present invention. In order to set the connection as shown in FIG. 14, the third configuration of the present invention having an extended cell and an extended cell output is required.

In FIG. 14, four connections C1, C2, C3 and C4 are input to the switch node having no flow control function. The peak rates are 0.
6, 0.3, 0.3 and 0.3. Similar to FIG. 13, the four connections are output from one output port having a switch node with the total peak rate being 0.6.

In FIG. 14, C2, C3 and C4 are first routed to the flow controller a of the present invention.
Here, the total bandwidth of these three connections is set to 0.
6, and outputs to the expanded cell output of the flow control device a. C2, C3, and C4 are input to the expanded cell input of the flow control device b, and the total peak rate is output as 0.6 through the switch node together with the connection C1 input from the cell input of the flow control device b.

In FIG. 13, the connections C2, C3, C
No. 4 had to have a peak rate of 0.3 or less. Since the peak rate of the path from the flow control device a to the flow control device b needs to be multiplexed together with the peak rate 0.6 of the connection C1 into one physical transmission line (cell input of the flow control device b), Because it was 0.3. For example, connection C2 is 0.6,
Assuming that C3 and C4 are each 0.15, FIG.
Since the output of the flow control device a of 0.3 is 0.3, the peak rate of 0.6 when the connection C2 is input cannot directly pass through this transmission line. By using the expanded cell input and the expanded cell output as shown in FIG. 14, such a problem is solved, and C2, C3, and C4 have a peak rate sum of about 0.9 or less for each connection. The peak rate can be set up to 0.6.

By the way, in FIGS. 12, 13 and 14,
Between the flow control device of the present invention and a device having a downstream flow control function, a switch node that cannot add congestion experience information to a data transmission cell, or write congestion information to a control cell or a buffer empty information transmission cell I was assuming there was a switch node that could not. In this case, it is necessary to set a predetermined quality assurance traffic parameter, for example, a limiting peak rate, in the flow control device of the present invention to control the traffic so that the switch node can guarantee the quality. There is.

All switch nodes between the flow control device of the present invention and a device having a downstream flow control function can add congestion experience information to a cell, and control cell or buffer empty information transmission cell contents. In the case of having the function of rewriting, the flow control device of the present invention works effectively even if a predetermined quality assurance traffic parameter is not set. The quality assurance traffic parameter is not given, and the cell output may be controlled only based on the buffer empty information transmission cells transferred from the downstream of the flow of the data transmission cells.

Next, an example of the functional configuration will be described below.
Next, a specific example of the functional configuration of each configuration of the present invention will be described. These are for explaining the logical configuration of the function, and may differ from the actual physical configuration. For example, if the required specification value regarding the throughput of the flow control device of the present invention is relatively small, the actual hardware can be configured by a memory, a processor, and a peripheral LSI, and the function can be implemented by software.

FIG. 15 shows an example of the functional configuration of the flow control device according to the first configuration of the present invention. The flow control device of the first configuration of the present invention has one cell input and one cell output. The cell input to the cell input is input to an appropriate buffer for each connection according to the connection identifier of the cell input in the connection identification unit. It may have a function of detecting that a cell having an incorrect connection identifier is input.

The buffer for each connection does not have a device having a downstream flow control function or a device having a downstream flow control function, which has a function of temporarily storing the data transmission cells transferred from the device having an upstream flow control function. This is because the reading of the buffer for each connection is controlled so that the buffer of the switch node does not overflow and the data transmission cells are discarded, so that the data transmission cells input from the cell input cannot always be immediately transferred to the cell output.

In the case of the credit system, basically,
An equal amount of buffer is allocated to all connections with flow control that pass through the flow control device of the present invention. This makes it possible to maintain fairness between connections. However, for a connection with a small cell flow rate, the buffer amount allocation may be dynamically changed by reducing the buffer amount allocated. The dynamic allocation function of the buffer amount in the switch node having the flow control function has been discussed by many researchers, and the discussion of the dynamic allocation mechanism of the buffer amount in the switch node is also applied to the flow control device of the present invention. It is applicable and will not be described here.

In the case of the rate control system, basically,
The buffer for each connection is shared and used by multiple (or all) connections. The cell stored in the connection-specific buffer is output from the cell output by the output scheduling unit under the control described later.

Information regarding the free area amount of the buffer for each connection is sent to the buffer free information generating means. The information regarding the amount of free buffer space is, for example: "N cells are output from the buffer for each connection, so that only N cells can be further stored in the buffer for each connection.""Number of cells stored in the buffer for each connection" Exceeds a certain number (or less than a certain number) "-" Target number that has a time ratio when the number of cells accumulated in the buffer for each connection is not zero when trying to read a cell " It is information such as "how much compared to the"-"cell transmission rate should be this (target cell transmission rate)".

When the congestion experience information is written in the cell, the information may be sent to the buffer availability information generating means. This information is, for example, information such as "no congestion has occurred (or congestion has occurred) in the switch node on the route from the device having the upstream flow control function".

When a control cell for congestion control is transferred in the same direction as the data transmission cell, the information may be sent to the buffer empty information generating means. This information is, for example: "No congestion has occurred (or congestion has occurred) at the switch node on the route from the device having the upstream flow control function". The number of cells stored in the buffer at the switch node on the route from the device
"How much time ratio is non-zero when trying to read a cell compared to a certain target value" -Current cell transmission rate of the connection in a device with upstream flow control function "-Control cell And so on.

In the case of the control method of transferring the "target cell transmission rate" to the device having the upstream flow control function,
The buffer vacancy information generating means calculates the transmission rate of the target cell by totaling the "current cell transmission rate".

The buffer empty information generating means creates a buffer empty information transmission cell based on these pieces of information. The buffer empty information transmission cell passes through the output scheduling unit and is output from the cell output. When the configuration is such that the control cell for congestion control is transferred from the upstream together with the data transmission cell, the cell may be looped back and output from the cell output. (This looped-back cell is also referred to as a buffer empty information transmission cell here.) Information about the buffer empty area amount of the flow control device of the present invention is written in the looped-back cell. The buffer empty information transmission cell is transferred to the device having the upstream flow control function of the present invention, and controls the traffic output from the device having the upstream flow control function.

As a method of transferring the buffer empty information transmission cell to the device having the upstream flow control function, for example,
The flow control device of the present invention assigns the connection identifier to
This can be easily realized by converting the connection identifier of the flow opposite to the flow of the data transmission cell from the upstream.

On the other hand, a buffer empty information transmission cell is transferred from a device having a flow control function downstream of the present invention to control traffic output from the flow control device of the present invention. The buffer empty information transmission cell is input from the cell input of the present invention, and transferred to the buffer empty information extraction means by the connection identification unit.

Buffer empty information extracted from the buffer empty information transmission cell by the buffer empty information extracting means is as follows:
It controls the transfer of the data transmission cells transferred to the output scheduling unit and output from the flow control device of the present invention. The control of the output scheduling unit is as follows.

For example, in the case where information is sent from a device having a downstream flow control function, "N cells have been output from the connection-specific buffer, so that only N cells can be stored in the connection-specific buffer". , The number of cells within N cells is sent to the connection. As a result, the device having the downstream flow control function does not overflow the buffer.

For example, the cell transmission rate for each connection from the flow control device of the present invention is reduced at a predetermined constant rate, and the "buffer for each connection" is set by the device having the downstream flow control function. The number of cells accumulated in is less than a certain number "or
When the information "congestion has not occurred in the switch node on the path to the device having the downstream flow control function" is sent, the cell sending rate of the connection is increased by a certain algorithm. As a result, the transmission rate can be increased within the range where the buffer overflow does not occur in the device having the downstream flow control function.

Also, for example, information about "how much compared with a certain target value in terms of time ratio when the number of cells stored in the buffer is not zero" is sent from a device having a downstream flow control function. If so, the ratio and the cell transmission rate of the connection are calculated to obtain a new cell transmission rate. As a result, it is possible to bring the time ratio at which the number of cells accumulated in the buffer for each connection in the device having the downstream flow control function becomes zero close to the target value.

Further, for example, when the information "set the cell transmission rate to this rate" is transmitted to the buffer empty information transmission cell, the cell transmission rate is set to be equal to or lower than that rate. As a result, cell discard can be prevented while improving the utilization efficiency of the route reaching the downstream switch node and the downstream flow control device.

When a control cell or a buffer vacant information transmission cell passes between the flow control device of the present invention and a device having a downstream flow control function, congestion information / rate information is sent to the cell according to the congestion state. If there are switch nodes that cannot be written, cells are discarded at these switch nodes so as not to be discarded as shown in FIG.
As already described with reference to Nos. 3 and 14, the total traffic of a plurality of connections output from the cell output of the flow control device of the present invention is controlled by the quality assurance traffic parameter (for example, the peak rate is limited). .
Basically, it suffices to set this traffic parameter by the number of devices having a flow control function downstream of the flow control device of the present invention. The control by the buffer empty information transmission cell is performed so as not to exceed the range controlled by this traffic parameter.

FIG. 16 shows an example of the functional configuration of the flow control device according to the second configuration of the present invention. In the second configuration of the present invention, the first configuration of the present invention described with reference to FIG. 15 is arranged in parallel. However, it is characterized by the control information transmission path at the time of transmission and reception of the buffer empty information transmission cell.

The buffer empty information transmission cell for controlling the data transmission cell output from the upper cell output of the second configuration of the present invention is input from the lower cell input as shown in FIG. On the other hand, a data transmission cell having the same connection as the data transmission cell and having a reverse flow is output from the lower cell output of the present invention, and the buffer empty information transmission cell controlling it is input from the upper cell input. To do. The buffer empty information transmission cell input from the cell input on one side has the buffer empty information extracted, and controls the output scheduling unit for cell output on the other side.

Further, the buffer empty information created by the empty information generating means for monitoring the buffer for each connection on one side is sent to the opposite side and transferred from the cell output on the opposite side as a buffer empty information transmission cell.

The setting of such a route has the following two advantages. First, the throughput of the data transmission cell is likely to be as high as the bandwidth of the physical link.
Since the connection in TM is bidirectional, using only one first configuration of the present invention can use up to about half the bandwidth of the physical link in one direction.
By routing flows in opposite directions of one connection to different cell inputs as in the second configuration of the present invention, it is possible to use up to the band of the physical link in each direction. The second reason is that, in the same connection, the route of the data transmission cell and the route of the buffer empty information transmission cell for controlling the data transmission cell of the flow in the opposite direction are the same, and therefore, the switch node having no flow control function. It is possible to set to pass the same route without distinguishing these cells in. As a result, when adding a routing tag for going to the flow control device in the switch node, there is an advantage that these cells can be added without distinction.

Although the buffers are separated on the upper side in FIG. 16, the effectiveness of the present invention does not change even if the same buffer resource is shared on both sides. Sharing has the advantage that a finite amount of buffers can be used more effectively.

FIG. 17 shows an example of the functional configuration of the flow control device according to the third configuration of the present invention. The third configuration of the present invention is obtained by adding two sets of extended cell input and extended cell output to the second configuration of the present invention described with reference to FIG.

The buffer empty information transmission cell for controlling the data transmission cell output from the upper cell output of the third configuration of the present invention is input from the lower cell input as shown in FIG. On the other hand, a data transmission cell having the same connection as the data transmission cell and having a reverse flow is output from the lower cell output of the present invention, and the buffer empty information transmission cell controlling it is input from the upper cell input. To do. The buffer empty information transmission cell input from the cell input on one side has the buffer empty information extracted, and controls the output scheduling unit for cell output on the other side.

The buffer empty information created by the buffer empty information generating means on one side is sent to the other side and transferred from the cell output on the other side as a buffer empty information transmission cell.

Similarly, regarding the relationship between the extended cell input and the extended cell output, the buffer empty information transmission cell for controlling the data transmission cell output from the upper extended cell output of the third configuration of the present invention is shown in FIG. Enter from the extended cell input on the lower side. On the other hand, a data transmission cell having the same connection as the data transmission cell and having a reverse flow is output from the lower expansion cell output of the present invention, and the buffer empty information transmission cell for controlling the same is the upper expansion cell input. Enter more.
The buffer empty information transmission cell input from the extended cell input on one side has the buffer empty information extracted, and controls the output scheduling unit for outputting the extended cell on the other side.

Further, the buffer empty information created by the buffer empty information generating means on one side is sent to the opposite side and transferred from the extended cell output on the opposite side as a buffer empty information transmission cell.

In FIG. 17, the buffers are separated on the upper side and the lower side, but the effectiveness of the present invention does not change even if both sides share the same buffer resource. ATM connections are bidirectional. In the first configuration of the flow control device of the present invention, bidirectional flows of the same connection are handled by the same flow control device. Further, the second and third configurations of the present invention are configurations in which the two first configurations are combined, and when a flow in a certain direction is passing through one side of the flow control device of the present invention. , The reverse flow of the same connection goes through the reverse side of the flow control device of the present invention.

FIG. 18 shows a functional configuration example of the fourth configuration of the flow control device of the present invention. This is a configuration in which the second configuration of the flow control device of the present invention described in FIG. 16 is halved and a buffer empty information interface unit is added. When only one flow control device of the present invention is connected to the switch node, the fourth configuration of the present invention is basically the same as the first configuration.

The fourth configuration of the present invention is such that the bidirectional flow of each connection can be handled by different flow control devices of the present invention, as shown in FIG. (The configuration is such that the same flow control device can be used.) As a result, when a plurality of flow control devices of the present invention are connected to the switch node, the flow of each connection is set when the connection is set. There is an advantage that restrictions on selecting a flow control device to be passed can be reduced. When setting a connection to a certain switch node, it is necessary to select which flow control device of the plurality of flow control devices is used to set the connection. As a policy to choose,
For example, the load on the cell output of each flow control device may be evenly distributed. By using the fourth configuration of the present invention, it is possible to freely select a flow control device capable of setting respective flows of bidirectional connections, and to distribute the cell output load of each flow control device as much as possible. There is an advantage that it can be done. Also, if multiple connections are set to a device with a downstream flow control function and traffic parameters for quality assurance are set for the traffic to the device with a downstream flow control function, The flow of a plurality of connections to the device having the flow control function needs to be output from one flow control device, so it is necessary to select the flow control device from this condition. Fourth of the present invention
The configuration of is excellent in this respect.

The operation of the fourth configuration of the flow control apparatus of the present invention when the control method using the control cell is used in the rate control method will be described below. The flow control method described here can also be realized by another configuration example of the present invention.

As an example, the payload of the control cell is: Direction Bits: Indicates after loopback. 2. Transmission rate: For devices with upstream flow control function,
Transmission rate of the connection at that time. 3. Explicit transmission rate: A request value "set to this transmission rate" to the device having the downstream flow control function and the device having the upstream flow control function calculated in the switch node through which the data transmission cell passes. A device having an upstream flow control function writes a desired transmission rate as an initial value. It is assumed that the information of is written.

The state of the buffer for each connection of the flow control device of the present invention is monitored by the buffer vacant information generating means (previous stage). Further, the buffer empty information generating means (previous stage) has a function of totalizing the transmission rates written in the control cells. The average transmission rate calculated based on the transmission rate written in the control cell that arrived when the buffer free space amount is smaller than a certain threshold value is too high than the ideal transmission rate, and the buffer free space amount is the threshold value. It is assumed that the average transmission rate calculated based on the transmission rates written in the control cells arriving at a larger time is too smaller than the ideal transmission rate. Based on such an idea, the "fair transmission rate" of the connection passing through the flow control device of the present invention can be calculated. Further, when there is a possibility that the buffer for each connection will overflow due to congestion, it is possible to prevent cell discard due to buffer overflow by setting this "fair transmission rate" to a significantly small value.

When the control cell arrives, if the explicit transmission rate written in the payload of the control cell is larger than the value calculated from the "fair transmission rate" (for example, 7/8), it is set in the explicit transmission rate area. Write the "fair transmission rate". In addition, the direction bit of the control cell is rewritten to a value indicating the cell after being looped back.

The control cell is transferred to the buffer empty information interface section. The buffer vacant information interface unit determines which flow control device a flow in the opposite direction in the same connection as the flow of the connection to which the arriving control cell belongs passes through, and the flow control device (flow control of its own) Transmission information (control cell in this example) in buffer empty information generating means
To transfer.

Upon receiving the information, the flow control device transfers it to the internal buffer empty information generating means (the latter stage) and transfers it to the output scheduling unit as a buffer empty information transmission cell. The buffer empty information transmission cell is immediately output from the cell output of the flow control device, and is transferred to the upstream device having the flow control function via the switch node.

In the switch node which does not have the flow control function passing in the middle of the transfer, the "fair transmission rate" of the data transmission cell is calculated, and the value and the explicit transmission rate of the buffer empty information transmission cell are An algorithm compares the values, and in some cases, the explicit transmission rate area is rewritten.

The flow control device which receives the buffer empty information transmission cell from the cell input transfers the cell to the buffer empty information extracting means. The difference between the control cell and the buffer empty information transmission cell can be identified by whether or not the direction bit of the payload has a value indicating that it is after loopback. The buffer free information extraction means extracts the explicit transmission rate as the buffer free information. The buffer empty information interface unit determines which buffer the buffer empty information transmission cell input to the flow control device controls the flow of the connection,
Transfer the buffer availability information (explicit transmission rate) to the flow control device (may be itself). Upon receiving the information, the flow control device transfers it to the output scheduling unit, and sets the cell transmission rate of the data transmission cell of the connection to be controlled to the value or less.

Further, the output scheduling unit outputs the control cell, in which the current transmission rate is written in the transmission rate area, from the cell output every time a fixed number of data transmission cells are transmitted for each connection.

The buffer empty information interface unit connects a plurality of flow control devices to each other and transfers the buffer empty information and the transmission information in the buffer empty information generating means to each other. The connection between the flow control devices can be easily realized, for example, by connecting the flow control devices to each other via a bus.

FIG. 19 shows a functional configuration example of the fifth configuration of the flow control device of the present invention. This is a configuration in which a flow control device input switch is added to the input side of the fourth configuration of the present invention described in FIG.

The fifth configuration of the present invention comprises a flow control device input switch on the input side. The cell routing in the flow control device input switch may be performed as follows, for example.

The identifier of the flow control device from which the cell is output is added to the cell. The flow control device input switch provided on the input side of the flow control device of the present invention is given the identifier of the flow control device of the present invention in advance, and is added to the cell input from the cell input or the extended cell input. If it matches the above identifier, the cell is routed inside the flow control apparatus of the present invention, and if it does not match, the cell is output to the extended cell output of the flow control apparatus of the present invention.

The flow control device of the present invention has an advantage that it is not necessary to have a table for each connection for managing such information by giving the cell the identifier of the flow control device to which the cell is output.

As a flow control device identifier given to the flow control device input switch in advance, a list of identifiers other than its own flow control device identifier is given, and only cells having the identifiers in the list are routed to the extended cell output. It may be configured. This has the advantage that even if the identifier added to the cell is incorrect, the cell will not go around indefinitely.

The fifth configuration of the flow control device of the present invention having the expansion cell input and the expansion cell output is by connecting a plurality of flow control devices of the present invention to each other by the expansion cell input and the expansion cell output. The traffic input to the cell input of the flow control device can be output to the cell output of another flow control device designated by the identifier written in the cell. Since the expanded cell input and the expanded cell output have a throughput that is a multiple of the cell input throughput, which is smaller than the number of the flow control devices of the present invention connected to each other by one, the non-blocking traffic is provided to each flow control device. Can be transferred. If non-blocking, no matter how the flow control input switch is routed, the cell input throughput and cell output throughput of all flow control devices can be made equal, and the flow control devices can be used efficiently. The advantage is that

From the above advantages, the fifth structure of the present invention is
Regarding the input, the flow of a plurality of data transmission cells is input in the form controlled by one quality assurance traffic parameter (for example, the peak rate is limited), and the output is also
This is effective in the case of a configuration in which the flow of a plurality of data transmission cells is controlled by one traffic parameter for quality assurance (for example, the peak rate is limited) and output. The flow of multiple connections controlled by a certain traffic parameter needs to be output from the same flow control device, so when considering various connection settings, they are input from one input port of the switch node. This is because it is necessary that the flows of a plurality of connections can be output from the cell outputs of different flow control devices.

FIG. 20 shows an example in which a network is constructed by combining a plurality of switch nodes to which the flow control device of the present invention is connected. The switch nodes are arranged in a ring shape, and the traffic of a plurality of flow-controlled connections between the switch nodes has a certain value (in FIG. 20, the peak rate is 0.
Determined in 6). The connection for connecting the terminals shares and uses this band for each ring between the switch nodes.
By configuring the network in this way, even if connection setting and release frequently occur, quality assurance traffic parameters given to the flow control device of the present invention (traffic between adjacent flow control devices of the present invention 20. It is not necessary to change the peak rate (0.6) in FIG.

Here, the connection form of the switch nodes on the ring is taken as an example, but the present invention also works effectively for other general networks. When a flow control mechanism is added to a switch node that does not already have a flow control function, the flow control function can be realized simply by connecting the flow control device of the present invention to the switch node. is there.

FIG. 21 shows an example in which the second configuration of the present invention is realized by using two slots of the backplane. The routing tag setting device is arranged in the path from the cell output of the flow control device of the present invention to the hardware switch, because the cell output from the flow control device of the present invention is output to the target output port of the switch node. This is for routing. The first, third, fourth, and fifth configuration examples of the present invention can be similarly realized. Thus, the present invention can be connected to the backplane of the switch node at the same interface as the interface board of FIG. That is, it is only necessary to connect to the same connector as the interface board. If the switch node has a hot-swap capability, a function can be added while the switch node continues to operate. When the cell buffer inside the switch board is about to overflow, the flow control device of the present invention may suppress the cell output via a backplane through a backpressure signal that does not use the cell. There is an advantage that the load on the switch board can be reduced at the time of congestion.

As another configuration, the flow control device of the present invention can be realized as a device that can be connected to an interface point. FIG. 22 shows an example in which two interface points are used to realize the second configuration of the present invention. The first, third, fourth, and fifth configuration examples of the present invention can be similarly realized. In this way, the configuration may be such that the connection is made to the end of the interface point via the physical transmission line.

Finally, an example of a method of determining a connection identifier when setting a connection via the flow control device of the present invention and an example of connection management in the flow control device of the present invention will be described. Here, in the physical transmission path between all switch nodes, the data transmission cell and the buffer empty information transmission cell for controlling the data transmission cell in the opposite direction of the same connection as that of the same VP
It has I and VCI and is transferred in the same route and in the same direction. It is assumed that the data transmission cell or the buffer empty information transmission cell (or control cell) can be identified by the payload type identifier (PTI) area of the ATM cell header. (It is assumed that the difference between the buffer empty information transmission cell and the control cell can be identified by the payload of the cell.) Further, the reverse flows of the same connection have the same VPI and VCI in the same physical transmission line, and the same. Route shall be transferred in the opposite direction.

In the flow control device of the present invention, it is necessary that a cell is provided with a connection identifier and the like. A configuration in which a connection identifier and the like are added to the beginning of the cell together with a routing tag when the cell is first input to the switch node, and is added before the cell is output from the switch node and transferred to the flow control device of the present invention. A method can be mentioned. The former has an advantage that it is not necessary to arrange a connection identifier setting function between the switch node and the flow control device of the present invention, and the latter has an advantage that the amount of additional information to be given to a cell transferred in the switch node can be reduced. There is an advantage that it can be reduced.

With the first configuration of the present invention as shown in FIG. 7, it is possible to know which flow is in the opposite direction of the same connection by the method described below. The first method is as follows: A connection identifier uniquely assigned in the flow control device to which the cell is output.

A connection identifier uniquely assigned in the flow control device to which a cell having a flow in the opposite direction of the connection to which the cell belongs is output. Is given. This has the advantage that there is no need to have a table for each connection that manages this information inside the flow control device of the present invention.

The second method is as follows: A connection identifier uniquely assigned in the flow control device to which the cell is output. It only gives. In this method, a table is managed inside the flow control device of the present invention. The table shows the connection identifiers: -A connection identifier uniquely assigned in the flow control device to which a cell in the reverse flow of the connection to which the cell belongs is output. Manage. This makes it possible to reduce the amount of additional information added to the cell. There are advantages.

For connections with the same connection identifier so that the correspondence can be easily understood, the upstream / downstream side is the same regardless of the flow direction, and the upstream / downstream identification bit is added to the cell. good.

With the second configuration of the present invention as shown in FIG. 8, it is possible to know which flow is in the opposite direction of the same connection by the method described below.

To a cell: A connection identifier uniquely assigned in the flow control device to which the cell is output. Is given. Since the reverse flows of the same connection are set to be output from different cell outputs of the upper and lower sides of the flow control device of the present invention, the same identifier can be assigned.
In this method, a small amount of information is added to the cell, and it is not necessary to manage the table as in the first configuration inside the flow control device of the present invention. In that respect, it is superior to the first configuration of the present invention. Simply, the buffer empty information transmission cell inputted from the cell input of one side (upper side or lower side) of the flow control device controls the connection having the same connection identifier outputted from the cell output of the opposite side. Even when the control cell is looped back, it is not necessary to rewrite the connection identifier. Further, the buffer empty information transmission cell for controlling the input traffic of the connection input to the cell input on one side has the same connection identifier as the data transmission cell and is output from the cell output on the opposite side.

With the third configuration of the present invention as shown in FIG. 9, it is possible to know which flow is the reverse flow of the same connection by the method described below.

In a cell: the identifier of the flow controller to which the cell is output.

A connection identifier uniquely assigned in the flow control device to which the cell is output. Is given. Since the reverse flows of the same connection are set to be output from different cell outputs of the upper and lower sides of the flow control device of the present invention, the same identifier can be assigned.

The buffer empty information transmission cell input from the cell input on one side of the flow control device controls the connection having the same connection identifier output from the cell output on the other side. Also, the buffer empty information transmission cell input from the expansion cell input on one side of the flow control device controls the connection having the same connection identifier output from the expansion cell output on the opposite side. In addition, the buffer empty information transmission cell for controlling the input traffic of the connection input to the cell input (or extended cell input) on one side has the same connection identifier as that of the data transmission cell, and the cell output on the other side (extended cell input). It is output from the expanded cell output).

The data transmission cell input from the cell input or the expansion cell input is output from the cell output or the expansion cell output of the flow control device of the present invention. Which one should output the data is written in the connection identifier of the cell. This can be easily determined by judging whether or not the identifier of the flow control device to which the cell is output matches the identifier of the flow control device.

Like the second configuration, the third configuration of the present invention also has the advantage that the table as in the first configuration and the upstream / downstream identification bits are not required. As shown in FIG.
With the fourth configuration of the present invention, it is possible to know which flow the reverse flow of the same connection passes through which flow control device by the method described below.

The first method is as follows: A connection identifier uniquely assigned in the flow control device to which the cell is output.

The identifier of the flow control device to which the cell of the reverse flow of the connection to which the cell belongs is output. -A connection identifier uniquely assigned in the flow control device to which a cell having a reverse flow of the connection to which the cell belongs is output. Is given. This has the advantage that there is no need to have a table for each connection that manages this information inside the flow control device of the present invention.

The second method is as follows: A connection identifier uniquely assigned in the flow control device to which the cell is output. Is given. In this method, a table is managed inside the flow control device of the present invention. The table shows the connection identifiers: The identifier of the flow control device to which the cell of the reverse flow of the connection to which the cell belongs is output.

A connection identifier uniquely assigned in the flow control device to which a cell having a flow in the opposite direction of the connection to which the cell belongs is output. Manage. This has the advantage that the amount of additional information added to the cell can be reduced.

With the fifth configuration of the present invention as shown in FIG. 11, it is possible to know which flow the reverse flow of the same connection is passing through which flow control device by the method described below. it can.

In the fifth configuration of the present invention, it is possible to know through which flow control device the reverse flow of the same connection passes through by the same method as the fourth configuration. The allocation of connection identifiers between switch nodes may be performed as follows. Multiple connections
In order to eliminate cell discard at a switch node that does not have a flow control function, if it is controlled by certain traffic parameters for quality assurance, by giving the same VPI to those connections, a switch node that does not have a flow control function. In the above, there is an advantage that routing can be performed by viewing only the VPI and traffic can be monitored. The embodiments of the present invention have been described above.

[0159]

As described above, according to the present invention, the flow control function can be easily added to a switch node or the like which does not have the flow control function. By adding the flow control device of the present invention to the switch node, it is possible to efficiently handle transfer data between computers without causing cell discard.

When the flow control device of the present invention is implemented, the flow control device of the present invention is connected to the backplane similarly to the interface board of the switch node, or the flow control device is connected to the interface point of the switch node. The function can be added without stopping the function of the operating switch node or disconnecting the already set connection.

Even if a flow control function based on a different system for each interface point is required, the flow control device of the present invention may be added in accordance with it, and various services can be provided at low cost. It will be possible.

Regarding the problem in the case where the transmission delay time of the cell is large in the method by the rate control for passing the connection with the flow control to the switch node which does not have the flow control function and the tunneling method, the flow control of the present invention is adopted. The solution is to divide and shorten the flow control section by connecting the device to a switch node that does not have an intermediate flow control function. Further, the problem that the efficiency is deteriorated by the tunneling method is solved by connecting the flow control device of the present invention to the switch node.

[Brief description of drawings]

FIG. 1 is a diagram showing a flow of cells via a flow control device according to the present invention.

FIG. 2 is a diagram showing a connection between the flow control device according to the first configuration of the present invention and a switch node.

FIG. 3 is a diagram showing a connection between a flow control device according to a second configuration of the present invention and a switch node.

FIG. 4 is a diagram showing a connection between a flow control device and a switch node according to a third configuration of the present invention.

FIG. 5 is a diagram showing a connection between a flow control device according to a fourth configuration of the present invention and a switch node.

FIG. 6 is a diagram showing a connection between a flow control device and a switch node according to a fifth configuration of the present invention.

FIG. 7 is a diagram showing a flow of cells via the flow control device according to the first configuration of the present invention.

FIG. 8 is a diagram showing a flow of cells via a flow control device according to a second configuration of the present invention.

FIG. 9 is a diagram showing a flow of cells via a flow control device according to a third configuration of the present invention.

FIG. 10 is a diagram showing a flow of cells via a flow control device according to a fourth configuration of the present invention.

FIG. 11 is a diagram showing a flow of cells via a flow control device according to a fifth configuration of the present invention.

FIG. 12 is a diagram showing a path of a data transmission cell passing through a flow control device of the present invention and a switch node.

FIG. 13 is a diagram showing a path of a data transmission cell passing through a flow control device of the present invention and a switch node.

FIG. 14 is a diagram showing a path of a data transmission cell passing through a flow control device of the present invention and a switch node.

FIG. 15 is a block diagram showing a functional configuration of a first configuration of the present invention.

FIG. 16 is a block diagram showing a functional configuration of a second configuration of the present invention.

FIG. 17 is a block diagram showing a functional configuration of a third configuration of the present invention.

FIG. 18 is a block diagram showing a functional configuration of a fourth configuration of the present invention.

FIG. 19 is a block diagram showing a functional configuration of a fifth configuration of the present invention.

FIG. 20 is a diagram showing an example of a form of a network that can be configured by the flow control device of the present invention and a switch node.

FIG. 21 is a schematic diagram illustrating a physical connection relationship between a flow control device of the present invention and a switch node.

FIG. 22 is another schematic diagram for explaining the physical connection relationship between the flow control device of the present invention and the switch node.

FIG. 23 is a schematic diagram illustrating a physical configuration of a switch node.

FIG. 24 is a diagram for explaining a problem of the conventional tunneling method.

[Explanation of symbols]

 1, 2 ... Device with flow control function 3 ... Switch node without flow control function 4 ... Flow control device

Claims (2)

[Claims] 1. A flow control device connected to an ATM switch having an ATM switch having at least a plurality of input ports and a plurality of output ports provided between ATM switches via a transmission line, wherein the plurality of inputs are provided. Among the ports, an ATM cell input from a specific input port is connected to an output port output via the ATM switch, and the ATM cell output from this output port is output to the next-stage ATM switch. As described above, a buffer for accumulating and storing the ATM cell connected to the input port for transmitting the ATM cell through the ATM switch to the output port connected to the ATM switch at the next stage, The first buffer vacant information transmission cell indicating the vacant information in this buffer is transmitted to the ATM switch in the preceding stage, The second port connected to the input port for transmitting the first buffer empty information transmission cell via the ATM switch to the output port connected to the ATM switch of the preceding stage, and the second port transmitted from the ATM switch of the next stage. Of the buffer empty information transmission cell and a control unit for controlling the output of the ATM cell from the buffer based on the buffer empty information of the transmission cell and a predetermined traffic quality assurance traffic parameter. apparatus. 2. An ATM switch having at least a plurality of input ports and a plurality of output ports provided between ATM exchanges via a transmission line, and an input from a specific input port among the plurality of input ports. The ATM cell of the next stage is connected to an output port which is output via the ATM switch, and the ATM cell output from this output port is output to the ATM switch of the next stage. Flow control for an ATM switch having a buffer for accumulating and storing the ATM cells connected to the input port for transmitting the ATM cells to the output port connected to the ATM switch via the ATM switch In the method, a first buffer empty information transmission cell indicating empty information in the buffer input to an input port is A
The ATM switch is controlled so that it is transmitted to the output port connected to the TM switch, and the buffer empty information of the second buffer empty information transmission cell transmitted from the ATM switch at the next stage and the predetermined transmission. A flow control method comprising controlling the output of the ATM cell from the buffer based on a quality assurance traffic parameter.